Silicon carbide (SiC) has a large energy band gap and high breakdown field. As such, SiC is an attractive material for electronic devices operating at high temperatures and high power. SiC also exhibits mechanical properties and chemical inertness which are useful in micro-electromechanical systems (MEMS) as well as nano-electromechanical systems (NEMS) for applications in harsh environments. SiC based devices are therefore particularly attractive for use as high-temperature sensors and actuators.
Additionally, SiC has a high acoustic velocity and extremely stable surfaces. Thus, SiC is a promising structural material for fabricating ultra-high frequency micromechanical signal processing systems. The highly stable physicochemical properties of SiC also improve the performance of high-frequency resonators as the surface-to-volume ratio increases when the resonator frequency scales into the GHz ranges.
One of the challenges in fabricating SiC devices is related to the selective etching of SiC films or SiC bulk materials. Unlike silicon (Si), SiC is not etched significantly by most acids and bases at temperatures less than about 600° C. Most wet etching processes, however, are not easily effected at temperatures greater than about 600° C. Non-standard techniques such as laser-assisted photo-electrochemical etching have been developed, but such techniques require special equipment and exhibit poor lateral dimension control.
Traditional fabrication processes incorporating photoresist etch masks are also problematic. Primary etch gasses that are used in SiC etching include chlorine (Cl2) and hydrogen bromide (HBr). The photoresist material, however, exhibits poor selectivity compared to SiC when exposed to traditional etch gases.
What is needed is a method of manufacturing a device incorporating a masking material which exhibits increased selectivity compared with traditional masking materials. What is further needed is a method of manufacturing a device incorporating a masking material which exhibits increased selectivity when exposed to traditional SiC etching gases.